The extinct Ngatutura volcanic field that was active between 1.54 and 1.83 million years ago [3][2] is one of four volcanic fields in an intraplate back arc relationship with the still active Hauraki Rift and the presently dormant Auckland volcanic field.[1] The other volcanic fields, which are part of the Auckland Volcanic Province, are the oldest, Okete to the south near Raglan in late Pliocene times (2.7-1.8 Ma).[4] and to the north the younger South Auckland volcanic field.[5]
| Ngatutura Volcanic Field | |
|---|---|
 Approximate limits of identified basaltic surface deposits associated with Ngatutura volcanic field. For more accurate maps see the literature.[1] | |
| Highest point | |
| Coordinates | 37°32′S 174°48′E / 37.54°S 174.80°E[1] |
| Geography | |
 Map showing Ngatutura Volcanic Field, but allowing wider volcanic context. Clicking on the map enlarges it, and enables panning and mouseover of volcano name/wikilink and ages before present. Key for the volcanics that are shown with panning is: basalt (shades of brown/orange), monogenetic basalts, undifferentiated basalts of the Tangihua Complex in Northland Allochthon, arc basalts, arc ring basalts, andesite (shades of red), basaltic andesite, and plutonic. White shading is selected caldera features. | |
| Geology | |
| Age of rock | |
| Mountain type | Volcanic field |
| Type of rock | Basalt |
| Last eruption | 1.6 Ma[1] |
Geology edit
This field is smaller than the other three and has far fewer basaltic volcanic centres. However at least 16 volcanic centres, mostly scoria cones associated with lava flows of limited hawaiite to nepheline hawaiite composition are known.[1] Some of the basalt deposits in this region of the coast are now known to be related to the West Ngatutura volcanic field with a stratigraphic age of c. 3.5 Ma around 60 km offshore.[2][5] The earlier work on the field had suggested fewer centres being:[6]
- Initial vent
- This was under the present sea but basaltic lava flowed to the east so is identifiable in present coastal stratigraphy.[6]
- Ohuka Centre
- Likely was a low angle scoria cone associated with an extensive basaltic lava flow of about 700 ha (1,700 acres).[6]
- Quarry Centre
- Two vents with limited basaltic extrusions, perhaps erupted along the Ohuka fault plane.[6]
- Ngatutura Complex
- Associated with at least five major phases of activity with evidence in nearby bays along the coast. Included some violent magmatophreatic eruptions[6]
See also edit
References edit
- ^ a b c d e Pittari, Adrian; Prentice, Marlena L.; McLeod, Oliver E.; Zadeh, Elham Yousef; Kamp, Peter J. J.; Danišík, Martin; Vincent, Kirsty A. (2021). "Inception of the modern North Island (New Zealand) volcanic setting: spatio-temporal patterns of volcanism between 3.0 and 0.9 Ma" (PDF). New Zealand Journal of Geology and Geophysics. 64 (2–3): 250–272. doi:10.1080/00288306.2021.1915343. S2CID 235736318.
- ^ a b c Bischoff, Alan; Barrier, Andrea; Beggs, Mac; Nicol, Andrew; Cole, Jim; Sahoo, Tusar (2020). "Volcanoes buried in te Riu-a-Māui/Zealandia sedimentary basins". New Zealand Journal of Geology and Geophysics. 63 (4): 378–401. doi:10.1080/00288306.2020.1773510. S2CID 221380777.
- ^ Briggs, R. M.; Itaya, T.; Lowe, D. J.; Keane, A. J. (1989). "Ages of the Pliocene—Pleistocene Alexandra and Ngatutura Volcanics, western North Island, New Zealand, and some geological implications". New Zealand Journal of Geology and Geophysics. 32 (4): 417–427. doi:10.1080/00288306.1989.10427549. hdl:10289/5260.
- ^ Nemeth, Karoly; Kereszturi, Gabor; Agustín-Flores, Javier; Briggs, Roger Michael (2012). "Field Guide Monogenetic volcanism of the South Auckland and Auckland Volcanic Fields". Retrieved 2 November 2022.
- ^ a b Bischoff, Alan; Barriera, Andrea; Begg, Mac; Nicola, Andrew; Colea, Jim; Sahoo, Tusar (2020). "Magmatic and Tectonic Interactions Revealed by Buried Volcanoes in Te Riu-a-Māui/Zealandia Sedimentary Basins". New Zealand Journal of Geology and Geophysics. 63: 378–401. doi:10.1080/00288306.2020.1773510. S2CID 221380777.
- ^ a b c d e Spratt, P. R. (1975). "The Ngatutura Volcanics, Southwest Auckland". Journal of the Royal Society of New Zealand. 5 (2): 163–178. doi:10.1080/03036758.1975.10419370.